Abstract

External parasitic infection remains one of the most common causes of disease in teleost and elasmobranch fish species under human care.^1,2,3 Unfortunately, the most commonly utilized antemortem screening technique for examination of the gills remains a gill biopsy, which is both a potentially dangerous technique and has poor sensitivity for many types of infection. Additionally, the anatomy of elasmobranch gills, as well as some teleost operculum configurations, makes traditional antemortem gill biopsy impossible. This is likely the reason why hands on diagnostics are commonly not performed even during quarantine, when the likelihood of animals having a pathogenic infectious disease is at its greatest.⁴

A strong candidate technique for improving gill examination of fish is rigid gill endoscopy. The technique is atraumatic and has a much higher sensitivity than traditional gill biopsy since it allows the clinician to examine the entire opercular cavity rather than only 5–10 primary gill lamellae. Endoscopically guided gill biopsy can also be performed to sample specific lamellae with potential pathology when gill endoscopy alone cannot identify a pathogen. The authors have successfully utilized rigid gill endoscopy for diagnosis of a large range of pathologies in teleost and elasmobranch fishes, including parasitic infections (including Ichythophtherius multifiliis, Cryptocaryon irritans, Amyloodinium spp., monogeneans, copepods, and leaches), anemia, acute and chronic gill trauma, telangectasia, and cellular hyperplasia. Additionally, the technique can be used in species with small opercular openings and recessed gill lamellae such as elasmobranchs or pufferfish. For these reasons, the authors would recommend adoption of gill endoscopy as part of normal quarantine procedures and moribund fish exams by any diagnostician with access to the technique.

Acknowledgements

The authors would like to thank the aquarists at the South Carolina Aquarium for their help with the medical care of the teleost and elasmobranch fish at the aquarium, and for their enthusiastic adoption of rigid gill endoscopy as part of the regular quarantine of their animals.

*Presenting author

Literature Cited

1.  Garner MM. 2013. A retrospective study of disease in elasmobranchs. Vet Path 50:377–389.

2.  Noga EJ. 2010. Fish Disease: Diagnosis and Treatment. Ames, Iowa: Wiley-Blackwell. 536 p.

3.  Boylan SM. 2019. Diagnosis of Fish Diseases. In: Smith SA, editor. Fish Diseases and Medicine. Boca Raton (FL): CRC Press. P 81–85.

4.  Hadfield CA, Clayton LA. 2011. Fish quarantine: current practices in public zoos and aquaria. J Zoo Wildl Med 42:641–650.